Police are looking for a man who groped a woman's bottom while she was running in the Hutt Valley.

Detective Sergeant Christiaan Barnard said the 22-year-old woman was indecently assaulted while running along the banks of the Hutt River between Melling Link and the Kennedy Good bridge about 3.30pm yesterday.

While running, the woman felt two hands touch her on the bottom, Mr Barnard said.

"On turning around an unknown male was running next to her and tried to start a conversation before touching her a second time.''

The woman ran from the man and reported the incident to police.

The offender was Maori, aged in his late teens, about 1.75m tall, of medium build and had short, shaggy hair.

He was wearing a white T-shirt and black shorts with a brown hoodie or jersey tied around his waist and black skate-style shoes.

Anyone with information should contact the Hutt Valley Police on 04 560 2600 or Crimestoppers on 0800 555111.